Until recently, I didn't pay much attention to the data that makes up my life—how many steps I take each day or miles I bike each week, how often I update my Facebook st
atus, feel stressed out, or have a drink.
A growing group of people do track this sort of data as part of the "quantified self" movement—everything from mood ratings to exercise routines to sleeping and eating habits. The idea is that this kind of tracking can teach us valuable things about ourselves and help us make better choices. Even if we think we know ourselves, the theory goes, tracking can yield surprises.
